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AWD Vs 4WD, What Is The Difference?

Ever got confused with acronyms like AWD and 4WD, and when went on to find what it is, even more terminologies come up to further confuse you, then give this a read to clear the fizz around these terminologies, and understand what should be the wise decision, when it is AWD vs 4WD.

With the SUV trend taking up the market by storm across the globe, manufacturers are trying their best to make healthy profits out of this Bodystyle. Taking into consideration of our domestic market, the SUV trend hasn’t brought in many SUVs as such. All we got are crossovers. Yeah, neither of us, the buyers or the manufacturers, don’t refrain ourselves from broaching them as SUVs, but they are crossovers. In our terminology, they aren’t even crossovers, since they do not offer basic mechanical hardware to power the all 4 wheels, even as an option. We’ll discuss more on, why these so-called SUVs do not stand true to the crossover tag sometime later. For now, let’s speak what’s the basic mechanical gear to power all four wheels and give you an AWD vs 4WD comparison here.

The AWD and 4WD systems are different all together, so one can easily decide between the two depending on their use.

AWD Vs 4WD Comparison

If you were ever in the market to buy a proper go-anywhere SUV or crossover or even love the high riding cars, you surely would have heard of these two acronyms, AWD and 4WD. And Yes! They would’ve confused you, so let’s make it easy. These are the terminologies used to differentiate or rather say classify the cars that can power their all four wheels. Let’s start with what’s different between the two, and how does AWD vs 4WD fair in terms of their application.

AWD Vs 4WD - What is All-Wheel-Drive?

In an AWD system, as the name goes, it manages power transmission to all the 4 wheels, all the time. Since, this system is mostly used on crossovers, which are meant to spend most of their life on the metaled tarmac and once in a blue moon attempt soft roading, only if the situation demands to do so. AWD systems, for the most part, power only two wheels of the cars, in short, the car is a front-wheel-drive vehicle unless the system detects a slip or loss of traction. And this is done with the help of a wheel speed sensor and assistance of an electronic rational clutch or a mechanical limited-slip clutch unit.

Confusing? Let it come with an example. Suppose you are driving down a road, there’s a patch of loose sand, the front wheels of the car runs out of traction. Now the power will be transmitted to the rear wheels. If it is an electronically controlled unit, then the sensor at wheels will detect the slip and send a message to the ECU or say the computer of the car, and ECU further actuates the electronic clutch unit to propel the rear wheels. In case of a mechanical limited-slip clutch, the spring-based clutches engage when they detect a slip.

In an AWD system, this transition from 2WD to 4WD happens automatically, but some manufacturers also offer an option to let this action happen only on demand by the press of a button. So for a larger duration of time, the AWD operate as front-wheel-drive cars, unless the system detects a need to intervene.

AWD Vs 4WD - What is 4-Wheel-Drive?

The 4WD systems are complex mechanical equipage built to take on terrains, where even trekking is a tough task. These systems are mechanically linked and come with an option to manually choose between the 2-wheel-drive mode and 4-wheel-drive mode. To make this happen, there is an extra gearbox known as Transfer Case. The transfer case performs two different functions, first, it lets the driver select between 2WD or 4WD layout, and second is it provides an extra set of gear ratio know as low-range. The low-range gearbox is an important component, as it gives the driver the leverage to opt for 4WD-low (4L). But its sole function is to increase the torque on offer to all wheels by the use of mechanical gears. This is how the Jeep Wrangler gets a crawl ratio of 84.2:1.

Toyota Fortuner comes equipped with a capable 4WD system, that comes equipped with a low-range box and transfer case.

The 4WD systems are user-operated, either by an electronic switch or a mechanical lever, to choose between the options of 2WD, 4WD or 4WD low. While there are cars offered with permanent or full-time 4WD layout, wherein the engine sends power to all the 4 wheels no matter what and the drivers can only change between 4H or 4L.

Designed to take over seriously played terrain; these systems can be mechanically upgraded to improve their capability, while AWD systems can only be tuned with their ECU or Traction control map. The 4WD systems can be had with solid axles at both ends, and equipped with differential lockers at the all the three differential, i.e. the center differential and those at the front and rear axles to send exact same power to all 4 wheels, contradicting the working principle of a differential.

The differentials are designed to work in a way, ‘it sends power to the wheel that has lesser road-friction’, why? Because this ability of a differential let the vehicle embarks a turn safely, by sending power to the outer wheel only. Though, this does hamper the vehicle’s capability to trace a washed-off trail. But, mechanical engineering is the most valued gift to mankind ever, produced differential lockers. These components are tactical as they sound, as they lock the differential. Yeah, they do lock the differential to zero, and thus there is no difference in the amount of power sent to both the wheels on an axle. This manifesto is also achieved at the transfer case by locking the center diff, thus rotating all the four wheels with the same power, torque and equal rotations per minute.

Buttons to lock the front, rear and centre diff. on a Mercedes-Benz G-Class.

These lockers can be electronically or pneumatically actuated. And, if that still sounds like a lot of work, then LSDs (No, not the drugs, Limited-Slip-Differential) can do it on its own. The LSDs make use of a spring-assisted clutch pack, which due to centrifugal force of slip between the two wheels, engage and lock the differential. The LSDs do have a slip associated with them, thus they are unable to lock the diff completely. To their upgrade, we now have mechanically locking diffs, seen on the Mahindra Thar, which also works the same way as the LSDs but instead of a clutch, it uses a mechanical locking component. The drawback with the MLD is they take a few seconds to engage and cannot be engaged manually and they do dis-engage themselves.

AWD Vs 4WD - What should you buy?

Chevrolet's guide to find out best suitable drive-train when the it always goes as AWD Vs 4WD.

If the basic requirement is to have increased traction in case of sporadic situations, like rain, snow, off-beaten path around the countryside, then AWD systems should be the right choice. With technical advancements, the AWD systems have become clever than ever and can give some untrained hands at 4WDs a serious competition. AWD cars are cheaper to buy and efficient to run, further increases their economic competency.

If words like Moab, Utah, Muck, ditch, ruts, and trails fantasize you, and the need to go Overlanding and taking on challenging terrain is what you can’t keep yourself away off, you know what you need, a proper 4WD SUV built with all mechanical ingredients to soup up its performance off the road.

Err, what’s possibly the best deal between AWD Vs 4WD?

A car that has got solid rigid axles with diff locks at both the ends and another locker at the centre differential with a potent transfer case. Ohh, that’s a Force Gurkha. But, if the serious off-roading trails are not in the checklist and wanderlust kicks you once or twice in a year, then understand that cars with potentially proven AWD systems and decent ride quality are in abundance, and cars like Renault Duster AWD or Jeep Compass can make for a good choice. Since capable 4WDs which also offer a cocooned ride with almost every creature comfort in existence are northwards of 35lac rupee mark and that’s an expensive car territory in the price-conscious Indian market. While the cars like Mahindra Thar and Force Gurkha are built to take you to the moon, drive around caters and back, but your back will survive this trip or not would still be a question. So, this was our AWD vs 4WD comparison. Stay tuned to IndianAuto.com for more such stories.